It has been investigated that a silicon-containing material is used as a negative electrode active material for lithium secondary batteries. In the case where the silicon-containing material is used as an active material, the active material is pulverized or is separated from a current collector because the volume of the active material expands or contracts when lithium is stored or is released. Therefore, there is a problem in that current collection in an electrode decreases and charge/discharge cycle characteristics deteriorate.
Patent Literature 1 discloses the use of a negative electrode in which the percentage of a binder in the vicinity of a negative electrode current collector is 2.5 times or more the percentage of the binder in a position away from the negative electrode current collector.
Patent Literature 2 discloses that the deformation of a current collector is suppressed and failures due to short circuits are reduced in such a manner that a silicon oxide represented by SiOx is used as an active material, SiOx with high oxygen concentration is placed on the current collector side, and SiOx with low oxygen concentration is placed thereon.